Method, computer program and driver assistance system for calculating predicted time before possible collision between two motor vehicles

Abstract

The invention relates to a method for calculating a predicted time (TTC) before a possible collision between a first motor vehicle (1) and an object (2), in which a driving envelope (6) of the first motor vehicle (1) is determined and the object (2) is represented by four corners (7r, 71, 8r, 81). Determining a pre-possible collision time (TTC) in a first case (S1) on the basis of an absolute first speed (v1) of the first motor vehicle (1) and irrespective of a second speed (v2) of the object (2) for a point in time within a time interval in which at least a part of the object (2) is located in the travel envelope (6), and determining the pre-possible collision time (TTC) in the first case (S1), on the basis of the absolute first speed (v1) of the first motor vehicle (1) and irrespective of the second speed (v2) of the object (2); in a second case (S2), a time (TTC) before a possible collision is determined on the basis of the relative speed between the first motor vehicle (1) and the object (2). Whether a first situation (S1) or a second situation (S2) is occurring is determined on the basis of the respective positions of the four corners (7r, 71, 8r, 81) relative to the driving envelope (6).

Description

Technical Field

[0001] The invention relates to a method for calculating a predicted time to a possible collision of a first motor vehicle moving in a first direction of movement with an object moving in a second direction of movement, wherein a travel envelope of the first motor vehicle is determined, the travel envelope describing a predicted area located in front of the first motor vehicle in the first direction of movement and through which the first motor vehicle will travel during a future movement of the first motor vehicle, wherein the object is represented by four corners forming a quadrilateral, which are divided into two front corners and two rear corners relative to the second direction of movement, and wherein the time to a possible collision is determined for at least one time point within a time interval during which at least a part of the object is located in the travel envelope. The invention also relates to a computer program and a driver assistance system. Background Art

[0002] Determining the time before a collision or the time before a possible collision is generally the basis for many driver assistance systems, which primarily have the purpose of collision warning or collision avoidance, such as automatic emergency brake assistance. Based on the calculated time before a collision, such driver assistance systems can take various measures accordingly, for example, they can warn the driver of an impending collision, or even actively intervene during driving, for example by automatic braking, to avoid such a collision. In order to determine such a time before a possible collision, first the driving envelope of the relevant motor vehicle can be determined, in which the aforementioned driver assistance system can be used, and in the present case, the motor vehicle is designated as the first motor vehicle. In the simplest case, this envelope can be provided by two straight lines, which extend in the current direction of movement of the first motor vehicle and are spaced apart from each other by a distance that approximately corresponds to the width of the first motor vehicle. For example, a prerequisite for a collision with an object is that the object will at least temporarily and at least to some extent stay within this driving envelope. The point in time of the stay must also additionally be within the time period in which the first motor vehicle reaches the location of the object. In order for the automatic emergency brake assistance system to determine whether the first motor vehicle will collide with the object, the time and distance when and where the collision occurs must be calculated. Based on the current movement of the first motor vehicle and the object, their future positions can be calculated and compared with each other in order to determine a potential collision point. This can be achieved by determining the position of each object (i.e., the first motor vehicle and the object) in multiple future time increments and comparing them. For example, for discrete future time increments, the position of the first motor vehicle and the object can be predicted. The interpolation between the last point before the collision and the point after the collision provides the collision time. This is described, for example, in the paper "Evaluation of Measurement and Prediction Uncertainty in Time-Based Intervention Decisions for Automatic Emergency Braking and Avoidance Systems" by Thomas Mauer of the University of Duisburg-Essen in 2013, which is published on the Internet at https: / / d-nb.info / 1034474758 / 34 and https: / / nbn-resolving.org / urn:nbn:de:hbz:464-20130508-152249-6.

[0003] This approach is very complex and therefore not suitable or at least not preferred for real-time computing.

[0004] Furthermore, the intersection of the trajectories can be used and based on the speeds of the motor vehicle and the object, it can be estimated whether both (i.e. the motor vehicle and the object) will arrive at the intersection at the same time. For the second method, in principle, many different collision configurations and scenarios must be considered, which makes the calculation more difficult. In particular, many different situations and special cases must be taken into account, each of which requires a different calculation mode. For example, in a simple intersection scenario, according to which the speeds of the vehicles are at 90° to each other when the objects are, for example, also vehicles, it is sufficient to use the absolute speeds to predict whether the motor vehicles will arrive at the intersection at the same point in time. On the other hand, for road users traveling parallel to each other and one after the other, relative speeds must be taken into account in order to calculate potential collisions.

[0005] In addition, Jiménez, F, Naranjo, JE and García, F, 2013, "Improved method for calculating the time to collision of two vehicles" (2013 Springer Publishing, International Journal of Intelligent Transportation Systems Research, Vol. 11, No. 1, pp. 34-42, DOI: 10.1007 / s13177-012-0054-4) describes various collision scenarios and the associated calculation possibilities of the corresponding time to collision. Here, it is necessary to distinguish a large number of cases, because the time to collision is calculated in different ways.

[0006] Furthermore, US 2013 / 0124041 A1 describes a method for assisting a motor vehicle driver in a driving maneuver, wherein at least the surroundings of the motor vehicle in the direction of travel are monitored in order to detect objects with which the vehicle may collide. In the event of an imminent collision with an object, the necessary steering or braking actions are indicated to the driver, or an automatic steering or braking action is performed. The contour of the vehicle body is taken into account to determine whether a collision with an object is about to occur. However, the time before the collision is not determined.

[0007] Furthermore, EP 2 837 538 B1 describes a system comprising: lane detection means for the driving lane and at least one adjacent opposing lane, a driver detection system for detecting the speed and position of another vehicle in the lane ahead of the vehicle relative to the vehicle, an overtaking detection means for determining when the vehicle has entered the opposing lane and is performing an overtaking maneuver, a vehicle detection system for detecting the relative position and speed of an oncoming vehicle in the opposing lane, and a collision assessment means for determining whether the overtaking maneuver can be safely concluded based on the relative speed and position of the vehicles. Based on the relative speed between the vehicle and the oncoming vehicle, the time until the two vehicles collide can be estimated. This time can then be compared with a limit value representing the possible time period that the vehicle still needs to complete the overtaking maneuver.

[0008] Here, determining the time before collision is simple, since only a single situation needs to be considered: vehicles approaching in the same lane.

[0009] However, in general, as mentioned above, there are many different collision scenarios. Summary of the invention

[0010] It is therefore an object of the present invention to provide a method, a computer program and a driver assistance system which allow the determination of the time before a possible collision to be determined most consistently in as many different collision scenarios as possible and to be described mathematically as simply as possible.

[0011] This object is achieved by a method, a computer program and a driver assistance system having the features according to the respective independent claims. Advantageous developments of the invention are subject matter of the dependent patent claims, the description and the drawings.

[0012] In a method according to the invention for calculating a predicted possible time before a collision of a first motor vehicle moving in a first direction of motion with an object moving in a second direction of motion, a travel envelope of the first motor vehicle is determined, the travel envelope describing a predicted area located in front of the first motor vehicle in the first direction of motion and through which the first motor vehicle will travel during the future movement of the first motor vehicle. Furthermore, the object is represented by four corners forming a quadrilateral, which are divided into two front corners and two rear corners relative to the second direction of motion; and for at least one time point within a time interval during which at least a part of the object is located in the travel envelope, a possible time before a collision is determined. In a specific first case, for at least one first time point during the time interval, the possible time before a collision is determined based on the current absolute first speed of the first motor vehicle at the first time point and without taking into account the second speed of the object; in a specific second case, for at least one second time point during the time interval, the possible time before a collision is determined based on the current relative speed between the first motor vehicle and the object at the second time point relative to the current first direction of motion at the second time point. Depending on the respective positions of the four corners relative to the travel envelope, it is determined whether this is the first case or the second case.

[0013] The invention is based on the recognition that collision scenarios can be divided into two types in principle, specifically scenarios in which it is sufficient to consider the absolute speed of the first motor vehicle to determine the time before a possible collision, and scenarios in which the relative speed between the first motor vehicle and an object, such as a second motor vehicle, must be considered. The invention is also based on the finding that in most cases, the respective situation can be classified as a first situation or a second situation based on the observation of the respective position of the corners of the object. For the special case in which the second direction of motion is perpendicular to the first direction of motion within the time interval, the absolute speed coincides with the relative speed, so that in this case it is not even necessary to distinguish between the two situations, and not even to depend on the position of the corners of the object relative to the travel envelope. Therefore, all possible situations, including this special case, can be simply divided into one of the two groups, and the time before the collision can be determined accordingly based on the absolute speed of the first motor vehicle or the relative speed between the first motor vehicle and the object relative to the first direction of motion. This advantageously allows the calculation of a time before a possible collision that is universal and can be applied to many different collision situations, in particular for parallel traffic and for directions of motion of the first motor vehicle and the object aligned at arbitrary angles relative to each other.

[0014] The object can in principle be any object, in particular any road user. However, the representation of the object by four corners is particularly suitable for objects that are depicted as vehicles, in particular motor vehicles, such as buses or trucks. Therefore, in the following, for the sake of simplicity and without limiting the generality, the object is also referred to as a second vehicle, in particular a second motor vehicle. The object can in particular be represented by four corners or points, which are theoretically connected to each other to form a convex quadrilateral, in particular a rectangle or a trapezoid.

[0015] As mentioned at the outset, in the simplest case, the travel envelope can be defined by two straight lines which are spaced apart from one another by a distance which corresponds to the width of the first motor vehicle. If, for example, the first motor vehicle is traveling in a curve, the travel envelope can also be represented, for example, by a boundary line extending in the form of a curve. Furthermore, it is conceivable to represent the travel envelope as a high-order polynomial by the boundary line, although this is not preferred due to the increased computational complexity. Furthermore, based on the movement parameters of the object, such as its speed and direction of movement, the trajectory or movement path of the object, in particular only such a second travel envelope, can be determined.

[0016] A prerequisite for a possible collision between two motor vehicles or between the first motor vehicle and the object can be, for example, the presence of an intersection area between the two driving envelopes. In addition, further conditions can be set for the time at which the individual vehicles reach the intersection area in order to calculate the collision as essentially as possible. However, in principle, the method relates to such a situation, in particular a collision situation, in which, at least for the case of non-parallel traffic, the object first reaches the intersection area, wherein reaching the intersection area is therefore equivalent to the object passing through or entering the driving envelope of the first motor vehicle. In other words, in the present case, only the time interval in which at least a part of the object is located in the driving envelope is taken into account. Therefore, in the present case, the predicted time before the possible collision is estimated, for example, at the earliest from the time point when the object first enters the driving envelope of the first motor vehicle, specifically from the first or second time point.

[0017] In addition, the predicted possible time before the collision is an estimated time, which may deviate from the actual time before the collision. In addition, as already mentioned, the predicted time describes a time period, which starts at a first or second time point within a time interval (within which the object is at least partially within the driving envelope) and ends at the time point of the theoretical collision.

[0018] Therefore, in the present case, the determination of parameters such as the first direction of motion, the second direction of motion, the first speed and the second speed, as well as the positions of the four corners relative to the driving envelope, and in particular the driving envelope itself, involves a calculation time, which corresponds to the time point at which the object enters the driving envelope at the earliest. As mentioned above, the determined time before the possible collision is correspondingly related to an initial time point, which is located within a time interval, during which at least a part of the object is located within the driving envelope. In order to simplify the description, the calculation time or the initial time point is selected as the current time point, and accordingly, the above parameters are also partially specified as the current first speed and the current second speed, the current positions of the four corners and the current first and second directions of motion, etc. However, it should be noted that this calculation time can also be a future time with respect to the current traffic scene. In other words, the actual current time point is located before the entry time of the object into the driving envelope. In this case, for example, it can be simply determined at which future time point, at which time, and where the object will enter the driving envelope, which can be predicted based on the current second direction of motion and the current second speed of the object. For this future time point, the future first direction of movement of the first motor vehicle can also be predicted in a corresponding manner based on the current first speed of the first motor vehicle and the determined current driving envelope range. For example, for an earlier collision prediction, the time required for the object to reach the driving envelope range of the first motor vehicle or to reach a specific position within the driving envelope range can also be additionally considered. This time can then be added to the time before a possible collision determined by the entry time into the driving envelope range, or generally added to the time before a possible collision determined starting from the first and / or second time point within the time interval. Therefore, in the following, without limiting generality, it is assumed that the current calculation time or the initial time point for calculating the time before the collision is within the time interval.

[0019] First of all, it is necessary to understand that there is still a period of time before a possible collision, so that by means of the optional, preceding method steps, it is possible to first evaluate or determine, for example, according to a predetermined criterion, whether a collision between the first motor vehicle and the object is at all possible. In the present example, it can be assumed that this is met. In addition, a possible collision can also be understood to mean that the collision does not necessarily have to occur, even if in principle there is a possibility that a collision will occur between the first motor vehicle and the object according to a predetermined criterion. For example, such a collision can be avoided by timely intervention of a driver assistance system, for example by outputting a warning to the driver, or by driving intervention, in particular steering and / or braking intervention. Therefore, the determination of the time before a possible collision is carried out under the following assumptions, that is, the current driving situation has not changed, and the first vehicle continues to move along the determined driving envelope range at its current first speed, and in particular, the object also continues to move in its second direction of motion according to its current motion parameters, such as its current second speed.

[0020] Whether at least a portion of an object is located in the driving envelope can be determined by very broad criteria. For example, if at least one corner representing the object is located in the driving envelope, it is determined that at least a portion of the object is located in the driving envelope. Furthermore, it can also be determined that an object is at least partially located in the driving envelope if at least two corners of the object are located on different sides of the driving envelope. Therefore, whether at least a portion of an object is located in the driving envelope can also be determined by taking into account the position of the corners of the object.

[0021] The fact that an object is represented by four corners should be understood as a mathematical representation of the object and not necessarily as a visual representation. Due to the representation of the motor vehicle by four corners, the calculations are greatly simplified, since a simplified geometric model of the object is provided in this way. In order to accurately determine the time before the collision, it is theoretically necessary to consider each individual contour point of the object. This can be simplified by the described process and advantageously also by considering four corners, more precisely four points, which represent the corners of the object. This is particularly advantageous for real-time applications.

[0022] The absolute speed or absolute first speed of the first motor vehicle is to be understood here as the magnitude of the first speed of the first motor vehicle in the first direction of motion. The relative speed between the first motor vehicle and the object with respect to the first direction of motion is to be understood here as the difference between the components of the first speed and the second speed that point to the first direction of motion. Thus, if, for example, the second speed has no component that points to the first direction of motion, for example in the case where the first and second directions of motion are perpendicular to each other, the relative speed corresponds to the absolute first speed. For example, if the first and second speeds are aligned in the same direction and parallel to each other, the relative speed is generated as the difference between the magnitude of the first speed and the magnitude of the second speed. If the first and second directions of motion are aligned parallel to each other and opposite to each other, the relative speed corresponds to the sum of the magnitude of the first speed and the magnitude of the second speed. In other words, the second speed has a speed component that points to the first direction of motion, and therefore, in order to determine the relative speed, the speed components of the first speed and the second speed that point to the first direction of motion are subtracted, and if these speed components are aligned opposite to each other, they are added.

[0023] In a further advantageous development of the invention, for the case in which the second direction of movement of the object, in particular the second motor vehicle, is oriented perpendicularly to the first direction of movement within the time interval, the time before collision or the time before possible collision is determined based on the current absolute first speed of the first motor vehicle, which corresponds to the current relative speed. In this case, the speed component of the second speed parallel to the first direction of movement is therefore zero. In this case, it therefore makes no difference whether the relative speed or the absolute first speed is used to determine the time before possible collision, since this leads to the same result. This case can therefore be assigned arbitrarily, for example randomly, to the first or second case.

[0024] In order to determine whether the directions of movement are perpendicular to one another or their angle or direction relative to one another, for example the speed of the first motor vehicle and its direction of movement, as well as the speed of the object and its direction of movement, can be detected, for example, by sensors, in particular vehicle surroundings sensors of the first motor vehicle. This information can then be provided accordingly to the control device of the first motor vehicle in order to calculate the time before the collision.

[0025] According to another advantageous refinement of the invention, if a possible collision has not yet occurred, the time before the possible collision is repeatedly determined for successive time steps. The calculation of the time before the collision is therefore repeatedly updated. For this purpose, updated captured data, such as the current first speed and / or the current second speed, and, for example, updated first and second directions of movement of the first motor vehicle and the object, are correspondingly captured and provided.

[0026] Thus, the time before a possible collision can be determined particularly accurately, even taking into account changes in current movement parameters of the first motor vehicle and of the object.

[0027] In a further advantageous refinement, for each time step, a classification is made as to whether this is the first case or the second case, depending on the current position of the four corners. Thus, in principle, each time step within the time interval can be assigned to one of the two defined cases. Accordingly, the time before collision is always determined as a function of the absolute first velocity or the relative velocity. It is therefore not necessary to define further cases for determining the time before collision. This greatly simplifies the calculation.

[0028] In a further advantageous development of the invention, the occurrence of the first or second situation is determined depending on the current position of the four corners, so that the classification as to whether this is the first or second situation depends on which of the four corners is located in the driving envelope. This has a great advantage, because in order to be able to classify the current situation as the first or second situation, it is only necessary to classify the individual corners as being within the driving envelope or as being outside the driving envelope. For example, if it is known that one of the specific corners is within the driving envelope, the exact position of this angle within the driving envelope is irrelevant. This further simplifies the calculation, because the position of the individual corners does not need to be known exactly, as long as it is at least able to determine with sufficient accuracy whether the corner is outside or within the driving envelope.

[0029] In another advantageous development of the invention, it is additionally determined whether this is the first or second situation, depending on whether the second direction of motion of the object within the time interval is at least partially directed toward the first direction of motion or is opposite to the first direction of motion. Thus, in order to classify the current situation as the first or second situation, in addition to considering the position of the angles or their position relative to the driving envelope, the alignment of the respective directions of motion of the first motor vehicle and the object relative to each other can also be considered. This consideration of the directions of motion relative to each other again allows a particularly simple distinction between the various situations, which will be explained in more detail later. Likewise, it is not necessary to know the exact angle at which the directions of motion are aligned relative to each other; it is sufficient to know whether the second direction of motion has at least partially a directional component opposite to or parallel to the first direction of motion. If it does not have this component, it again corresponds to the special case in which the first and second directions of motion are aligned perpendicularly to each other. As mentioned above, since it is not important for this special case to perform the calculation by considering the absolute speed or the relative speed, it is also not necessary to consider this case further below. Thus, all collision scenarios can be divided into two groups again, depending on whether the second direction of motion is oriented at least proportionally opposite to the first direction of motion or at least proportionally parallel to the first direction of motion.

[0030] In another advantageous development of the invention, for the case in which the second direction of motion of the object at least partially points in the same direction as the first direction of motion within the time interval, this is determined to be the first case if or as long as none of the rear corners of the representation of the object is located in the driving envelope and the rear corners are located on the same side of the driving envelope, and this is determined to be the second case if or as long as a connecting line connecting at least one rear corner or at least a part of one of the rear corners is located in the driving envelope. The fact that the connecting line connecting the rear corners is located in the driving envelope corresponds to the two rear corners being located on different sides of the driving envelope. The aforementioned connecting line in turn corresponds to the mathematical model representation of the object. As mentioned above, such a connecting line is not necessarily taken into account. This is because such an imaginary connecting line is located in the driving envelope when the two rear corners of the object are located on different sides of the driving envelope. This is particularly true, for example, when the second motor vehicle is traveling directly in front of the first motor vehicle in the same direction of motion and is much wider than the first motor vehicle, so that the rear corners of the second motor vehicle are located on both sides outside the driving envelope of the first motor vehicle. In addition, in this case, all corners of the second motor vehicle can be located outside the driving envelope of the first motor vehicle. Since a collision is still possible, it can be detected that the corners of the second motor vehicle or the object are located on different sides of the driving envelope. Accordingly, the object is also partially located in the driving envelope and a collision is possible. In this case, the relative speed between the two vehicles must also be taken into account when determining the time before a possible collision. Therefore, if the second direction of movement and the first direction of movement are at least partially aligned, which means that the object is moving in a direction away from the first motor vehicle, then, when determining the time before a possible collision, only the absolute speed of the first motor vehicle needs to be taken into account as long as none of the rear corners of the object is located in the driving envelope and the rear corners are also located on the same side of the driving envelope. In all other cases, when the rear corners are located on different sides of the driving envelope or at least one rear corner is located in the driving envelope, the relative speed must be taken into account. This allows a particularly simple differentiation by taking into account the corners of the objects and the respective directions of movement relative to each other.

[0031] In a further advantageous development of the invention, for the case where the second direction of movement of the object at least partially opposes the first direction of movement within the time interval, this is determined to be the first case if or as long as none of the represented front angles of the object is located in the driving envelope and the front angles are located on the same side of the driving envelope, and this is the second case if or as long as at least one front angle and / or at least a portion of the connecting line connecting the front angles is located in the driving envelope. The fact that the connecting line connecting the front angles is again located in the driving envelope corresponds to the fact that the two front angles are located on different sides of the driving envelope. Thus, for the case where the first and second directions of movement are at least partially opposed to one another, which means that the object is traveling in the direction of the first motor vehicle, only then can the absolute speed of the first motor vehicle be used to determine the time before a possible collision, as long as none of the represented front angles of the object is located in the driving envelope and the front angles are also located on the same side of the driving envelope. As soon as one of the front angles enters the driving envelope or the front angles are located on different sides of the driving envelope, the relative speed must be taken into account, since the relative distance between the first motor vehicle and the object decreases with the speed of the object in the direction of the first motor vehicle.

[0032] For example, if the above-mentioned special cases of perpendicular alignment of the first and second movement directions and parallel alignment of the first and second movement directions relative to each other are also assumed, the time interval can always be divided into two partial intervals, wherein the first case occurs once and the second case occurs once.

[0033] Therefore, according to another advantageous improvement of the present invention, it can be provided that, at least when the second movement direction of the object is neither completely perpendicular nor completely parallel to the first movement direction, the time interval is divided into two partial intervals depending on which of the four corners is currently located in the driving envelope range; wherein, in the first partial interval of the two partial intervals, this is the first case, and the time before the collision is correspondingly determined according to the current absolute first speed of the first motor vehicle, regardless of the current second speed of the object; in the second partial interval of the two partial intervals, this is the second case, which means that the time before the collision is correspondingly determined according to the relative speed between the first and second speeds.

[0034] In the case of perpendicular alignment of the directions of motion relative to one another, as described above, it is not important whether the calculation is carried out with absolute or relative speeds, and in the case of parallel driving, the relative speed must always be taken into account, which means that the entire time interval must be taken into account. Thus, the different collision scenarios can be divided in a very efficient manner and in principle into two cases, which in turn allow a particularly efficient calculation of the time before the collision. The two possible cases are further divided based on the consideration of the position of the corners of the object, in particular relative to the travel envelope. Depending on the respective classification of these corners, it can therefore be decided whether this is the first case in which only the absolute speed must be taken into account, or the second case in which the relative speed must be taken into account.

[0035] In another advantageous development of the invention, the time before the collision is additionally determined based on the current distance between the first motor vehicle and the object, in particular the shortest distance, in particular the distance along the driving envelope. However, it is also possible to approximate the shortest direct distance between the first motor vehicle and the object. Since the current consideration occurs in any case in a very short period of time before the collision, this distance is usually also very short, so that whether the distance is considered as a direct distance along a possibly curved driving envelope or as a so-called straight-line distance between the first motor vehicle and the object, there is no difference, at least no significant difference. In the case where the driving envelope extends along a straight line, this does not make any difference in any case. The distance can be determined, for example, by suitable sensors of the first motor vehicle. In addition, for other parameters used to calculate the possible time before the collision, suitable sensors for detecting these parameters can be provided, in particular as part of the first motor vehicle. Therefore, if the possible time before the collision is determined by a control device associated with the first motor vehicle, it represents another advantageous development of the invention, and the current first speed, the second direction of motion relative to the first direction of motion, the distance to the object and in particular the second speed are provided as input variables to the control device, in particular for each time step. The control device is therefore provided with all the variables required for calculating the time until possible collision and can perform the calculation as described above.

[0036] As already described, sensors of the first motor vehicle can be used to provide these calculation parameters. Thus, if sensor data relating to the object are provided, in particular captured, by at least one environmental sensor of the first motor vehicle, a second direction of movement relative to the first direction of movement, a distance to the object and in particular a second speed are determined from these data, which represents a further very advantageous refinement of the invention. The first speed can be provided by a speed sensor of the first motor vehicle. In any case, this is usually determined in the first motor vehicle and can therefore also be provided to the control device in order to calculate the time before the possible collision.

[0037] In another advantageous development of the invention, the movement path of the object is determined, and an intersection area of ​​the movement path with the driving envelope is determined, wherein the time point at which the first motor vehicle arrives at the intersection area is determined, wherein a collision is classified as possible when this time point is after the entry time of the object into the driving envelope and before the exit time of the object leaving the driving envelope. This can be used as the predetermined criterion described at the beginning in order to classify potential collisions as actually possible collisions. If this is not the case, this does not necessarily mean that a collision is impossible. However, if necessary, other or further considerations must be provided. As also already mentioned, within the scope of the present invention, collisions that occur when an object is already within the driving envelope are mainly considered. For example, when an object is about to enter the driving envelope, it is not considered that the object will hit the first motor vehicle.

[0038] Furthermore, the invention relates to a computer program comprising instructions which, when executed by a computing unit, cause the computing unit to carry out a method according to the invention or one of its embodiments.

[0039] Furthermore, a data carrier on which a computer program according to the invention or one of its embodiments is stored shall also be regarded as belonging to the invention.

[0040] The invention furthermore relates to a driver assistance system for a motor vehicle, wherein the driver assistance system is designed to carry out the method according to the invention or one of its embodiments. The driver assistance system can, for example, comprise the aforementioned computing unit running a computer program or a data carrier according to the invention or one of its embodiments. Furthermore, the driver assistance system can also comprise the aforementioned vehicle environment sensors or other possible sensors for providing calculation parameters and calculation variables.

[0041] Furthermore, the driver assistance system can be configured, for example, as an emergency brake assistance system. A configuration as a collision warning system or the like is also conceivable. Depending on the determined time before a possible collision, the driver assistance system can issue a warning to the driver or perform automatic braking of the first motor vehicle, for example, when the determined time before a possible collision is less than a limit value.

[0042] Furthermore, a motor vehicle having a driver assistance system according to the invention or one of its developments is also to be regarded as belonging to the invention.

[0043] Further features of the invention can be found in the claims, the drawings and the description of the drawings. The features and combinations of features mentioned in the above description and the features and combinations of features mentioned in the following description of the drawings and / or shown individually in the drawings may be used not only in the respectively indicated combination but also in other combinations without departing from the scope of the invention. Therefore, embodiments of the invention which are not explicitly shown and explained in the drawings, but which emerge and result from the explained embodiments by means of an individual combination of features, should also be considered to be included and disclosed. Therefore, embodiments and combinations of features which do not have all the features of the initially formulated independent claims should also be considered to be disclosed. Furthermore, embodiments and combinations of features which go beyond or deviate from the combinations of features outlined in the backward references to the claims should be considered to be disclosed, in particular disclosed by the above-described embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The exemplary embodiments of the present invention will be described below with reference to the accompanying drawings. In the drawings:

[0045] Figure 1 shows a schematic diagram of a first motor vehicle and a second motor vehicle at different points in time to illustrate a method for calculating a time before a collision according to an exemplary embodiment of the present invention;

[0046] Figure 2 Shows Figure 1 A schematic diagram of a motor vehicle in which the motor vehicle and a second motor vehicle are in another traffic situation according to an exemplary embodiment of the present invention;

[0047] Figure 3 Shows Figure 1 A schematic diagram of a motor vehicle in FIG. 1, wherein the motor vehicle is in another traffic situation with a second motor vehicle according to an exemplary embodiment of the present invention; and

[0048] Figure 4 Shows Figure 1 Schematic diagram of a motor vehicle in which the motor vehicle is in another traffic situation with a second motor vehicle according to an exemplary embodiment of the invention. DETAILED DESCRIPTION

[0049] Figure 1A schematic diagram of a first motor vehicle 1 and an object 2, which in this example is also formed as a second motor vehicle 2, at two different points in time t1, t2 is shown to illustrate a method for calculating a predicted time before a possible collision of a first motor vehicle 1 with a second motor vehicle 2 according to an exemplary embodiment of the invention. The first motor vehicle 1 also has a control device 3 as part of a driver assistance system 4 of the motor vehicle 1, wherein the control device is designed to carry out the method described below for calculating a time before a possible collision TTC, wherein a possible collision will also be referred to below in short as a collision to some extent. In addition, the driver assistance system 4 can also include at least one vehicle environment sensor 5 of the motor vehicle 1. Based on the sensor data provided by the vehicle environment sensor 5, information about the environment 9 of the motor vehicle 1 and in particular also of the second motor vehicle 2 can be provided to the control device 3. In order to determine whether there is a risk of collision, the control device 3 can first determine a driving envelope 6 of the first motor vehicle 1. The driving envelope 6 is bounded in a lateral direction by two boundary lines 6a, 6b, which lateral direction means perpendicular to the current direction of movement. In this example, the current direction of movement of the first motor vehicle 1 is represented by the x direction shown. The motor vehicle 1 continues to travel in the x direction at a speed v1. The travel envelope 6 has a width in the y direction which corresponds to the width of the motor vehicle 1. The travel envelope 6 thus describes the predicted area to be covered during the future movement of the motor vehicle 1. If an object is present in this travel envelope 6, for example, at least partially in this example, the second motor vehicle 2, a collision with such an object is accordingly possible.

[0050] By means of the sensor 5, which can be, for example, a lidar, a radar, an ultrasonic sensor and / or a camera, a second motor vehicle 2 can be detected in the environment 9 of the motor vehicle 1. In addition, it can be determined whether or when the second motor vehicle 2 enters the driving envelope 6 of the first motor vehicle 1. During the time interval in which at least a part of the second motor vehicle 2 is located in the driving envelope 6, the control device 3 accordingly calculates the time TTC before the expected collision with the second motor vehicle 2 in corresponding consecutive time steps (for example, the time steps t1, t2 shown here by way of example). This will be described in more detail below.

[0051] Firstly, for this purpose, the second motor vehicle 2 can be mathematically modeled and represented by its four corners 7l, 7r, 8l, 8r. All corners 7l, 7r, 8l, 8r of the second motor vehicle 2 do not always have to be detected by the sensor 5 or visible to the sensor 5 at the same time. When not all of these corners 7l, 7r, 8l, 8r are detected, the calculation method described below can also be performed. However, it is advantageous to detect at least one of the front corners 7l, 7r and one of the rear corners 8l, 8r and represent the second motor vehicle 2 with them. In addition, the connecting line between the front corners 7l, 7r is denoted by 7 in this example.

[0052] exist Figure 1 , the motor vehicle 2 moves at a speed v2 in the second direction of movement R2 and in the process crosses the driving trajectory of the first motor vehicle 1 at an angle. Accordingly, the second motor vehicle 2 crosses the driving envelope 6 of the first motor vehicle 1. At the first time step t1, only the right front corner 7r of the second motor vehicle 2 is located in the driving envelope 6. If the second motor vehicle 2 continues to drive in the second direction of movement R2, then eventually the left front corner 7l will also enter the driving envelope 6, and then the right front corner 7r will leave the driving envelope 6 again on the opposite side, and the same is true for the left front corner 7l, and then the right rear corner 8r will enter the driving envelope 6, as shown in FIG. Figure 1 As shown in the second time step t2 in , the same is then true for the left rear corner 81, after which, in a corresponding manner, the two rear corners 8r, 81 will also leave the driving envelope 6 again one after another on the opposite side. At least in this case, even if no collision with the first motor vehicle 1 occurs during this period.

[0053] In this example, the second direction of movement R2 is at least partially opposite to the first direction of movement R1 of the first motor vehicle 1. In other words, the speed v2 of the second motor vehicle 2 has a speed component v2' that is opposite to the speed v1 of the first motor vehicle 1. As a result, as soon as the front angles 7l, 7r of the second motor vehicle 2 (in this case the right angle 7r) enter the driving envelope 6, the distance a1 gradually decreases with the further driving of the second motor vehicle 2, even if the first motor vehicle 1 is no longer moving forward. This distance a1, which corresponds to the first time point t1 in the present case, decreases due to the forward driving of the second motor vehicle 2 until at least one of the front angles 7l, 7r is located in the driving envelope 6. If, on the other hand, both front angles 7l, 7r have left the driving envelope 6 again on the opposite side and if the motor vehicle 2 is moving forward, no further reduction of the distance occurs due to the further movement of the motor vehicle 2. This distance corresponding to the second time point t2 is denoted here by a2. Therefore, as long as or as soon as the front corners 71, 7r are outside the driving envelope 6, the vehicle 2, in particular its rear corners 81, 8r, can be considered to be stationary. In this case, the reduction in distance a2 can only be attributed to the speed v1 of the first motor vehicle 1. In this case, which is also referred to as the first situation S1 below, the time before collision TTC can therefore be determined solely based on the absolute speed v1 of the first motor vehicle 1, which is simply expressed in this example as:

[0054] TTC=a2 / v1.

[0055] However, in the aforementioned situation, also referred to below as the second situation S2, the time before collision TTC must be determined as a function of the relative speed between the first and second motor vehicles 1 , 2 , for example as a function of:

[0056] TTC = a1 / (v1–v2').

[0057] This applies when no change of situation occurs within the time TTC before a possible collision (in this example, from the second situation S2 to the first situation S1). Otherwise, the determined time TTC before a collision can also consist of individual time segments determined corresponding to the respective situations S1, S2.

[0058] The relative speed therefore represents the difference between a first speed v1 of the first motor vehicle 1 and a component v2 ′ of a second speed v2 of the second motor vehicle 2 which is parallel to the first speed.

[0059] Figure 2Another illustration of a traffic situation with a first vehicle 1 and a second vehicle 2 is shown. These vehicles 1, 2 and in particular the driver assistance system 4 can be designed as already described above. In this case, the direction of movement R2 of the second motor vehicle 2 is oriented so that the speed v2 of the second motor vehicle 2 has a component v2' oriented parallel to the first speed v1, which component v2' points in the same direction as the first direction of movement R1 of the first motor vehicle 1. The second motor vehicle 2 is again shown for two time steps t1, t2, wherein the second time step t2 is located temporally after the first time step t1. Here, the vehicle 2 is also represented by its respective angles 7l, 7r, 8l, 8r, and the connecting line between the rear angles 8r, 8l is represented by 8. As long as the rear angles 8l, 8r and their connecting line 8 are outside the driving envelope 6, the second motor vehicle 2 can be assumed to be stationary, because no reduction in the distance a1 to the first motor vehicle 1 due to the movement of the second motor vehicle 2 occurs. Thus, in this example, the shortest distance a1 to the second motor vehicle 2 is always at the position of the second motor vehicle 2 along the lower boundary line 6b of the driving envelope 6. However, this situation changes as soon as the rear corners 81, 8r (in this example, the left rear corner 81) enter the driving envelope 6 or reach the boundary line 6b. From this point on, the distance a2 to the motor vehicle 1 decreases further due to the movement of the second motor vehicle 2. Figure 2 The situation shown on the right corresponds to Figure 1 The first case described, in which, for calculating the time before collision TTC, only the absolute speed v1 of the first motor vehicle 1 needs to be taken into account; while the second motor vehicle 2 shown on the left corresponds to the absolute speed v1 of the first motor vehicle 1. Figure 1 A second situation S2 is described in which, when calculating the time to collision TTC, the speed or speed component v2 ′ of the second motor vehicle 2 must also be taken into account.

[0060] Thus, depending on whether it is situation S1 or S2, the time TTC before the collision can be simply calculated according to one of the above formulas. Thus, in general, depending on whether it is situation S1 or S2, the time TTC before the collision or the possible individual time segments constituting the time TTC before the collision can be calculated only according to the absolute speed v1 of the first motor vehicle 1 or according to the relative speed between the first and second motor vehicles 1, 2. Depending on the second direction of movement R2 relative to the first direction of movement R1, and depending on the position of the individual corners 7l, 7r, 8l, 8r of the second motor vehicle 2, it can be simply determined which of the two situations S1, S2 is the case. Thus, if the second direction of movement R2 is at least partially opposite to the first direction of movement R1, and if both front corners 7l, 7r are not located within the driving envelope range 6 and are located on the same side of the driving envelope range 6, this is the first situation S1, otherwise it is the second situation S2. On the other hand, if the second direction of movement R2 is at least partially aligned with the first direction of movement R1, this is a first situation S1, as long as the rear angles 81, 8r are not within the driving envelope 6 and the rear angles 81, 8r are also located on the same side of the driving envelope 6. Otherwise, this is a second situation S2.

[0061] Thus, the total time interval during which the second vehicle 2 is at least partially located in the envelope 6 can be divided into, for example, two partial time intervals, one of which can be assigned to the first situation S1 and one to the second situation S2. This is applicable at least when the first and second vehicles 1, 2 are not traveling absolutely parallel to each other and not perpendicular to each other. These situations will be described below.

[0062] Figure 3 Another special case is shown. Here again, the first and second motor vehicles 1, 2 are shown, which can also be designed as described above. In this example, the width of the second motor vehicle 2 is such that none of its corners 7l, 7r, 8l, 8r are located within the driving envelope 6. However, the motor vehicle 2 is at least partially located within the driving envelope 6, so a collision is possible. Since in this case the first and second directions of movement R1, R2 are parallel to each other, the relative speed between the two vehicles 1, 2 must also be taken into account in order to determine the time before collision TTC. The second case S2 therefore occurs here again. In this case, although the rear angles 8l, 8r are not located within the driving envelope 6, the rear angles 8l, 8r are not on the same side of the driving envelope. In other words, here, the connecting line 8 connecting the rear angles 8l, 8r is therefore located at least partially within the driving envelope 6. The distance between the two motor vehicles 1, 2 is indicated here by a0.

[0063] Figure 4Another traffic situation is shown with a first motor vehicle 1 and a second motor vehicle 2, which can likewise be designed as described above. In this example, the second direction of movement R2 is also parallel to the first direction of movement R1 and is also aligned with the first direction of movement.

[0064] The second motor vehicle 2 is now much smaller than in the previously described example, so that now the corners 71, 7r, 81, 8r or at least one rear corner 81, 8r are also arranged in the driving envelope 6. In particular, in this example, the second vehicle 2 is traveling exactly parallel to the first motor vehicle 1 in the same lane in front of the first motor vehicle 1. In the event of a collision, the first motor vehicle 1 will first collide with the rear corners 8r, 81 of the second motor vehicle 2. The rear corners 81, 8r are already in the driving envelope 6 and will be the last to leave the driving envelope 6. Therefore, the time interval in which the relative speed must be taken into account in order to calculate the time before collision TTC represents the total time interval in which the second vehicle 2 is at least partially in the envelope 6. Accordingly, in this example, the second situation S2 occurs again, in which the relative speed between the two vehicles 1, 2 must be taken into account in order to determine the time before collision TTC. Here, the distance between the two motor vehicles 1, 2 is also denoted by a0.

[0065] Therefore, at least when the situation does not change during the time before a possible collision TTC, the determination or calculation of the time before a collision TTC may be constituted as follows:

[0066]

[0067] a represents the distance between the first and second motor vehicles, which is Figure 1 and Figure 2 In is shown by a1 and a2, and in Figure 3 and Figure 4 is shown by a0, |v1| is the magnitude of the first velocity v1, |v2| is the magnitude of the second velocity v2, and α is Figures 1 to 4 : is the angle in the counterclockwise direction between the first speed v1 and the second speed v2 shown in , or between the speed vectors representing these speeds.

[0068] The situation in which the second motor vehicle 2 will, for example, cross the travel envelope 6 perpendicularly (corresponding to an angle α=90°) can be interpreted as the first situation S1 or the second situation S2, since this will lead to the same result. In other words, in this case, only the absolute speed of the first motor vehicle 1, namely v1, is equally relevant. In other words, in the case of a crossing at an angle of 90°, the second vehicle 2 is therefore traveling at an angle of 90° relative to the first vehicle 1. This relative speed is therefore equal to the absolute speed v1 of the first vehicle 1. Therefore, for both time intervals, the results obtained are the same as if the calculation had been performed taking into account only the absolute speed v1.

[0069] Furthermore, it should be noted that when the second vehicle 2 leaves the driving envelope 6 laterally, the relative speed of the second motor vehicle 2 cannot be reasonably calculated for the last intersection point between the second motor vehicle 2 and the driving envelope 6, because the vehicle 2 has left the driving envelope 6 and the time before collision TTC (which exists in the future) will not result in a collision.

[0070] In summary, these examples show how, with the aid of the present invention, an efficient calculation of the time before collision can be provided for an automatic emergency brake assist function by using the absolute and relative speeds of a potentially extended target vehicle. The advantage of the present invention is that a discretized prediction of the position along the vehicle trajectory can be avoided, which is very time-consuming and memory-intensive; while still being able to follow a general algorithm for calculating the time before collision. For the definition of the time interval, only two cases need to be considered, and both time intervals can then be calculated in a general manner.

Claims

1. A method for calculating a predicted time to collision (TTC) between a first motor vehicle (1) moving in a first direction of movement (R1) and an object (2) moving in a second direction of movement (R2), comprising the following steps: determining a travel envelope range (6) of the first motor vehicle (1), the travel envelope range (6) describing a predicted area located ahead of the first motor vehicle (1) in the first direction of movement (R1) and through which the first motor vehicle (1) will travel during future movement of the first motor vehicle (1); The object (2) is represented by four corners (7r, 7l, 8r, 8l) forming a quadrilateral, the four corners being divided into two front corners (7r, 7l) and two rear corners (8r, 8l) relative to the second movement direction (R2); Determining the time before a possible collision (TTC) for at least one time point within a time interval in which at least a portion of the object (2) is located within the driving envelope (6); It is characterized in that in a specific first situation (S1), for at least one first point in time during the time interval, determining the time before a possible collision (TTC) based on a current absolute first speed (v1) of the first motor vehicle (1) at the first point in time and without taking into account a second speed (v2) of the object (2), and in a particular second situation (S2), for at least one second point in time during the time interval, determining the time before a possible collision (TTC) based on a current relative speed between the first motor vehicle (1) and the object (2) relative to the first direction of movement (R1) at the second point in time, Wherein, whether the vehicle is in the first situation (S1) or the second situation (S2) is determined according to the corresponding positions of the four corners (7r, 7l, 8r, 8l) relative to the driving envelope range (6).

2. The method according to claim 1, characterized in that For the case in which, within the time interval, the second direction of movement (R2) of the object (2), in particular the second motor vehicle (2), is oriented perpendicularly to the first direction of movement (R1), the time before a possible collision (TTC) is determined based on the current absolute first speed (v1) of the first motor vehicle (1), the current absolute first speed (v1) corresponding to the current relative speed.

3. The method according to any one of the preceding claims, characterized in that If a possible collision has not yet occurred, the time before a possible collision (TTC) is determined repeatedly for consecutive time steps (t1, t2).

4. The method according to claim 3, characterized in that For each of the time steps (t1, t2), a classification is performed as to whether the first situation (S1) or the second situation (S2) is in accordance with the current position of the four corners (7r, 71, 8r, 81).

5. The method according to any one of the preceding claims, characterized in that Based on the current positions of the four corners (7r, 7l, 8r, 8l), the existence of the first situation (S1) or the second situation (S2) is determined, so that depending on which of the four corners (7r, 7l, 8r, 8l) is located in the driving envelope range (6), the first situation (S1) or the second situation (S2) is classified.

6. The method according to any one of the preceding claims, characterized in that In addition, whether the first situation (S1) or the second situation (S2) is determined based on whether the second movement direction (R2) of the object (2) within the time interval is at least partially directed toward the first movement direction (R2) or is opposite to the first movement direction (R1).

7. The method according to any one of the preceding claims, characterized in that For the case where the second movement direction (R2) of the object (2) within the time interval at least partially points in the same direction as the first movement direction (R1), if none of the represented rear angles (8r, 8l) of the object (2) is located in the driving envelope range (6) and the rear angles (8r, 8l) are located on the same side of the driving envelope range (6), it is determined that the first situation (S1) is occurring; if a connecting line (8) connecting at least one rear angle (8r, 8l) or at least a part of one of the rear angles (8r, 8l) is located in the driving envelope range (6), it is determined that the second situation (S2) is occurring.

8. The method according to any one of the preceding claims, characterized in that For the case where the second movement direction (R2) of the object (2) within the time interval is at least partially opposite to the first movement direction (R1), if none of the represented front angles (7r, 7l) of the object (2) is located in the driving envelope range (6) and the front angles (7r, 7l) are located on the same side of the driving envelope range (6), it is determined that the first situation (S1) is occurring; if at least one of the front angles (7r, 7l) and / or at least a portion of the connecting line (7) connecting the front angles (7r, 7l) is located in the driving envelope range (6), it is determined that the second situation (S2) is occurring.

9. The method according to any one of the preceding claims, characterized in that At least when the second movement direction (R2) of the object (2) is oriented neither completely perpendicularly nor completely parallel to the first movement direction (R1), The time interval is divided into two partial intervals depending on which of the four corners (7r, 7l, 8r, 8l) is currently located in the driving envelope range (6), wherein, in the first of the two partial intervals, the first situation (S1) is in place, and In the second partial interval of the two partial intervals, the second situation (S2) is in place.

10. The method according to any of the preceding claims, characterized in that The time to collision (TTC) is determined based on a current distance, in particular a shortest distance (a1, a2, a0), between the first motor vehicle (1) and the object (2), in particular along the driving envelope (6).

11. The method according to any one of the preceding claims, characterized in that A movement path of the object (2) is determined, and an intersection area between the movement path and the driving envelope range (6) is determined, wherein a time point at which the first motor vehicle (1) reaches the intersection area is determined, wherein when the time point is located after an entry time of the object (2) entering the driving envelope range (6) and before an exit time of the object (2) leaving the driving envelope range (6), the collision is classified as a possible collision.

12. The method according to any one of the preceding claims, characterized in that The time before a possible collision (TTC) is determined by a control device (3) associated with the first motor vehicle (1), the current first speed (v1), the second direction of movement (R2) relative to the first direction of movement (R1), the distance (a1, a2, a0) to the object (2) and in particular the second speed (v2) being provided as input variables to the control device, in particular for each time step (t1, t2).

13. The method according to any of the preceding claims, characterized in that By means of at least one vehicle environment sensor (5) of the first motor vehicle (1), sensor data about the object (2) are provided, based on which the second direction of movement (R2) relative to the first direction of movement (R1), the distance (a1, a2, a0) to the object (2) and in particular a second speed (v2) are determined.

14. A computer program comprising instructions which, when executed by a computing unit (3), cause the computing unit (3) to carry out the method according to one of the preceding claims.

15. A driver assistance system (4) for a motor vehicle (1), wherein: The driver assistance system (4) is designed to carry out the method according to one of claims 1 to 13.

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